Isothermal carburization

As a result of fliese temperature - programmed runs, additiond experiments were conducted isothermally at temperatures between 723 - 873 K. Based on tbe second phase peak (peak 2), the conversion - time profiles at different temperatures exhibited a characteristic Sigmoid shape and may therefore be used to interpret the solid carburization kinetics. As detailed in Brown [5], the transient convrasion data may be d cribed by... 

Hofer, L. J. E., Cohn, E. M., and Peebles, W. C. 1949. Isothermal decomposition of the carbide in a carburized cobalt Fischer-Tropsch catalyst. J. Phys. Coll. Chem. 53 661-69. 

The reduced catalysts were carburized under either isothermal or temperature-programmed conditions at 1 atm. Unless otherwise stated, the carburizing gas was a mixture of H2 and CO (H2/CO = 3 by volume). 

An additional series of measurements were carried out under isothermal conditions at 1 atm (Figure 2). For these experiments, carburization of the hydrogen-reduced catalysts was limited to a period less than six hours. The data, analyzed in terms of the parabolic rate law, exhibit two distinct regions of carburization (Figure 3). The parabolic rate constants were calculated from the initial and final slopes (Table III). The parabolic rate constants yield the activation energies and preexponential factors summarized in Table IV. 

Magnetization Resulting from Carburization. Thermomagnetic analysis (TMA) identified magnetite as the only ferromagnetic phase in the unreduced catalyst, and iron in the reduced samples. TMA measurements were made after isothermal carburization and after temperature-... 

Table III. Parabolic Rate Constants for Isothermal Carburization of Catalysts B-2 and B-6...

For the isothermal carburization of catalysts B-2 and B-6, the TMA results (Table VI) exhibit the following trends ... 

Fig. 5. Weight percent of original organic matter converted to aqueous C2-C5 mono-carboxylic acids after hydrous pyrolysis of aliquots of Kreyenhagen, Monterey, and Phosphoria Retort shales isothermally heated at temperatures from 240 to 365 for 72-h durations. Experiments were conducted in carburized stainless steel-316 reactors in the authors laboratory...

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